remove fn_data from event handler signature

examples/webui-push-ws/main.c

@@ -10,7 +10,7 @@
 static const char *s_listen_on = "http://localhost:8000";
 static const char *s_web_root = "web_root";
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_HTTP_MSG) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_http_match_uri(hm, "/api/watch")) {
@@ -21,7 +21,6 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
       mg_http_serve_dir(c, ev_data, &opts);
     }
   }
-  (void) fn_data;
 }
 
 // Push to all watchers